There are two vacuum motors used to control outlet airflow direction.
Item # 1 in the diagram is the PANEL-DEFROST motor, item # 20 is the PANEL/FLOOR door.
If #1 is stuck in the defrost position, you will get airflow from the defrost, but only when the second door is not in the full floor position. If you switch the selector to FLOOR, the defrost airflow should cease.
Need to know whether this is the case or not before giving the next step.
The vacuum motors are controlled by the head unit, whether manual or electronic.
There are two screws that tighten the vacuum
Just because those are tightened doesn’t mean the vacuum plug is fully pushed in. To ensure proper connection grab the center of the vacuum plug and push the entire vacuum plug towards the climate control
There is a 3-way vacuum valve located behind the battery next to the firewall be sure to inspect it. The replacement seal for it is quite cheap and will eliminate the chance of it being faulty.
Sometimes one of the vacuum lines is corroded or punctured which will result in ‘defrost only mode’ as this is the climate controls safe mode to ensure no further damage is done.
Here is what the vacuum line looks like on some models. In the previous illustration, this would be the vacuum line that goes into the actuator (1).
